1. Field of the Invention
The present invention relates to boresight alignment issues in bidirectional fiber coupled systems with asymmetric fiber core diameters, e.g., free space optical communication systems, and more specifically, it relates to techniques for combining and separating the optical output from multimode and single mode fiber coupled sources.
2. Description of Related Art
Free space optics (FSO) is a telecommunication technology that uses light propagating in free space to transmit data between two points. The technology can be useful where the physical connection of the transmit and receive locations is difficult. For example, in cities, the laying of fiber optic cables can be expensive and, in some instances, impractical based upon the infrastructure already built.
Free space optics can also be used to communicate between spacecraft, since outside of the atmosphere there is little to distort the signal. Such systems can also be used in aircraft if the system is designed to track the position of the first location (e.g., the vehicle) with respect to the position of the second location (e.g., a ground station receiver or transceiver). In some instances, the optical links use infrared laser light. Communication is also possible using light emitting diodes (LEDs) or other light sources, in some systems. The beams of light in FSQ systems are transmitted by light focused on receivers. These receivers can, for example, be telescopic lenses able to collect the photon stream and transmit digital data. The data can be any item of information that can be transmitted on a communication system. For example, types of data can include one or more application programs (i.e., sets of executable instructions), files to be executed by such programs, or data, among other types. Files to be executed can, for example, take the form of Internet messages, video images, radio signals, or computer files, among other items.
Boresight alignment of dual core fiber ports has been a significant issue in free space optical communications systems. It is desirable to simplify the current optical systems and to significantly reduce their weight and power usage. It is also desirable to improve the performance of the current systems.